Deflection circuit for cathode-ray oscillographs



Sept. 16, 1952 I M. NADIR DEFLECTION CIRCUIT FOR CATHODE-RAY OSCILLOGRAPHS Filed Nov. 1, 1950 2 SHEETS SHEET 1 IN VEN TOR. MA RK NA 0/ R M +PIA A T TORNEYS Sept. 16, 1952 NAD|R 2,611,105

DEFLECTION cmcun' FOR CATHODE-RAY OSCILLOGRAPHS Filed Nqv. 1, 1950 ZSHEETS-SHEET 2 BY p ATTORNEYS Patented Sept. 16 1952 Mark Nadir, New York, N. Y., assignor to Allen I B. Du Mont Laboratories, Inc., Clifton, N. a-

corporation of Delaware Application November 1, 1950, Serial No. 193,3 7.?

This invention relates to a new and improved circuit for use with a cathode ray tube. By means of this circuit the beam of the cathode ray tube is caused to produce a circular trace on the screen thereof having a diameter which may be adjusted and upon which may be impressed one or more signals as desired.

It is often desired to portray a phenomenon on the screen of a cathode ray tube by means of a display on a circular trace upon which timing markers may also be super-imposed. A circular scan has an advantage of being approximately three times as long as a conventional horizontal scan for the same diameter tube face. It is particularly advantageous when phenomena in connection with rotating machinery are to be observed, and instantaneous angular positions determined by means of synchronized timing or position markers. Phase splitting circuits hitherto used are not operable over a wide range of rotational speeds or frequencies and for extremely low speeds become impractical because of the physical size of the components required.

Accordingly, it is an object of this invention to provide means for producing signals which when applied to the deflection plates of a standard cathode ray tube cause the beam thereof to trace a circle on the fluorescent screen thereof.

It is a further object to provide a circuit to which a plurality of signals'may be applied to cause indications to appear on the circular trace.

Additional objects will become apparent after studying the specification in connection with the drawing, in which the single figure on two sheets is a schematic diagram of one embodiment of the invention.

In the drawing, Fig. 1, there is shown a potentiometer I, to one side of which a lead carrying signals from a source of signals 9 to be displayed is connected, the other side being grounded. The contact arm of this potentiometer is connected to the grid of an amplifier tube 2 through a grid current limiting resistor 3. A plate load resistor 4 is connected between the plate and a source of potential and a cathode bias resistor 5 is connected between the cathode and ground.

A potentiometer 6 is connected between two resistors 1 and 8 and this series combination is connected between a source of positive potential and ground. The movable contact of this potentiometer is connected through a resistor 8 to the grid of tube II. This grid is also connected to a source of timing signals ID.

The cathode of tube II is also connected to the cathode of a mixer tube l2 and to ground 2 Claims. (Cl. 315-24) 2 through a resistor 13, and. its plate is connected directly to a source of positive potential.

The output of the amplifier tube 2 is connected through a non-linear resistive element It to the grid of the mixer tube l2 which is also connected to ground throughresistor iii. The use of this non-linear elementas a coupling element results in a non-linearity which partly'compensates for the non-linearity of a modulator tube l! to which the output voltage developed across plate load resistor I6 is connected.

' The cathode of this modulator tube I! is connected directly to the plate of an oscillator tube i8 connected as a conventional oscillator, which may oscillate, forexample, at a frequency in the vicinity of 5 megacycles. Since the plate of the oscillator'derives its power from the cathode of tube ll, tube ll acts as a, modulator.

The output of theoscillator coil [9. taken from the rid end thereof, is fed through lead 20 into four capacitive voltage divider circuits formed by the combinations of capacitors 24,25, 26 and 21 with capacitor 28, respectively (shown inFig. la). Capacitor 28 is a special form of variable capacitor in which the elements 'vary the capacity sinusoidally and in which there are four rotors or stators spaced electrical degrees apart. It is mechanically driven by shaft 3|] in synchronism at some multiple, which may be unity, with the machinery to be observed and with the source of timing signals [0. The voltages appearing at points A, B, C, and D are fed to rectifiers 3|, 32, 33, and 34, respectively. The D. C. voltages developed in these rectifiers are filtered and applied directly to the grids of D. C. amplifier tubes 35, 36, 31 and 38,

At this point, suitable D. C. voltages may be added to position and center the beam of the cathode ray tube by means of potentiometers 4| and 42 for the X-axis, and potentiometers 43 and 44 for the Y-axis, in a manner well known to the art.

The plates of the D. C. amplifier tubes 35 and 36 are connected directly to the X-axis deflection plates 45 and 46 respectively of the cathode ray tube 50, while the plates of the D. C. amplifier tubes 31 and 38 are connected directly to the Y- axis deflection plates 41 and 48, respectively.

The operation is as follows:

A signal, or a plurality of signals to be displayed, which may be derived from rotating machinery, indicated in block form at 9, are applied to the input potentiometer I, amplified by amplifier 2 and applied to the grid of mixer tube [2. At the same time, a steady D. C. voltage, conat the plate of the mixer tube I2. In additionthere is a signal due to the application to the grid of the signal from tube 2.

These signals are applied directly to the grid-oi the modulator tube l1 and serve to vary the potential applied to the oscillator tube 18, thu changing the output accordingly.

The modulated output applied to the capacitive D. C. voltage applied by potentiometer '6. This is faithfully transmitted through all the amplifiers because of than C. connections- The input signal and the timingmarkers alsoarotransmitted and cause the beamto'be-defleeted out wardly with a positive signal applied.

The timing markers being synchronized with the rotating condenser serve, if rotating machinery is being observed,.to indicate accurately the instantaneousangular position ofgtheprim mover which drives the ,mechanicalsystemh It is to be understood that these .t. ni1ng markers may be produced at .a multiple orsubemultiple of the prime mover or special capacitor 28 jor reater precisionof measurement. It is alsoito be understood that the special capacitor 28 maybe driven at a multiple orsub-multipleof .thepr'ime mover so that a portion-of the cycle or several cycles of theprime mover vmaybedisplayed over 360 on the tube face, appropriate beamLblanking being applied to minimizeiconfiision,

While a preferred embodiment of the invention has been described, other embodiments may be apparent without departing from the spirit and scope thereof as defined in the appended claims.

What is claimed is:

1. In a cathode ray oscillograph, a cathode ray tube a mix rci cu ourceof ignals connected to sa d mi ert rcu peolr'ce' gti e ee signals connected to said mixer circuit, and a source of unidirectional potential adjustable in magnitude also connected to said mixer circuit, a modulatortub e, a radio frequency oscillator, the output of said mixer circuit being connected to said modulator tube to modulate said oscillator,a cyclically variable capacitive voltage divider, the

outputyef.said zosoillator being connected to said voltage divider producing four output voltages with a ninety degree phase relation existing therebetween, a rectifier connected to said voltage divider, an amplifier connected. to said rectifier and to the four deflection plates of said cath- Q'deray tubeto cause hebeam thereof tod scribe a. circu ar trace on the s reen, 116reof.., the min s 1. said ci cu ar trace. bei g variable in accordan e ith sa d dius ablepotent al t p ovide a ai oular base line, said signals and said. timing signals each producing a change insaidradiusg 2. The device of claim 1 including-.anon-linear e istance eleme t c nnected ibetwe niseid source of sig and i m xercireuit to com ensate 0rl 9n+1in ri yo s idmodu ator tube- R FERENGES GITED The following references are of record the file of this patent: 3 a

UNITED STATES 7 PATENTS Ensel a dt. g 5 3919; 1. 

